This invention applies to the field of light fixture lenses and more particularly to the square or rectangular lens panels used as diffusers on fluorescent light fixtures. Such lenses are often installed into recessed or surface-mounted fluorescent light fixtures, or are made to rest on the flanges of the T-bar grid openings that are illuminated from above.
Some prior art light fixture lenses are simply white opal translucent plastic sheets or prismatic light control patterns. All such prior art lenses have three short-comings.
First, all fluorescent lamps emit significant UV (ultraviolet radiation) that is harmful to humans, as well as damaging to photosensitive materials, such as textiles, documents and other organic materials. Most prior-art fluorescent lenses do not have enough thickness to stop such radiation.
Second, all fluorescent lamps emit significant IR (infrared radiation) that is uncomfortable to humans, as well as damaging to heat sensitive materials, such as paintings, painted wood, animal specimens and other organic materials that are subject to being dried out. Most prior-art fluorescent lenses do not have enough thickness to stop such radiation.
Third, prior-art lenses tend to accumulate internal dirt and dead insects that are attracted to the light and remain trapped in the fixture until they die and fall onto the inner surface of the lenses, making the fixtures look dirty and unsightly.
The first purpose of the present invention is to provide a lighting lens capable of blocking UV radiation. The second purpose of the invention is to provide a lighting lens capable of blocking IR radiation. The third purpose of the invention is to provide a lens in which trapped debris particles and dead insects are not visible.
The foregoing purposes are achieved by a dual-surface lens for light fixtures and T-bar ceilings in which a first lens panel has a planar perimeter around a central area of decorative or optical control and a second lens panel has a planar perimeter resting on the planar perimeter of the first lens panel. In a preferred embodiment the central area of the first lens panel is flush with or depending below the planar perimeter and the second lens panel is pyramidal and extending above the planar perimeter at an angle of 5xc2x0 to 15xc2x0.